orbital tumours and tumour-like lesions: exploring the ... · pictorial review orbital tumours and...

PICTORIAL REVIEW

Orbital tumours and tumour-like lesions: exploringthe armamentarium of multiparametric imaging

Bela S. Purohit1 & Maria Isabel Vargas2 & Angeliki Ailianou1& Laura Merlini1 &

Pierre-Alexandre Poletti1 & Alexandra Platon1& Bénédicte M. Delattre1 &Olivier Rager3 &

Karim Burkhardt4 & Minerva Becker1

Received: 1 September 2015 /Revised: 3 October 2015 /Accepted: 8 October 2015 /Published online: 31 October 2015# The Author(s) 2015. This article is published with open access at Springerlink.com

Abstract Although the orbit is a small anatomical space, thewide range of structures present within it are often the site oforigin of various tumours and tumour-like conditions, both inadults and children. Cross-sectional imaging is mandatory forthe detection, characterization, and mapping of these lesions.This review focuses on multiparametric imaging of orbitaltumours. Each tumour is reviewed in relation to its clinicalpresentation, compartmental location, imaging characteristics,and its histological features. We herein describe orbital tu-mours as lesions of the globe (retinoblastoma, uveal melano-ma), optic nerve sheath complex (meningioma, optic nerveglioma), conal-intraconal compartment (hemangioma),extraconal compartment (dermoid/epidermoid, lacrimal glandtumours, lymphoma, rhabdomysarcoma), and bone and sinuscompartment (fibrous dysplasia). Lesions without any typicalcompartmental localization and those with multi-compartment involvement (veno-lymphatic malformation,plexiform neurofibroma, idiopathic orbital pseudotumour,IgG4 related disease, metastases) are also reviewed. We

discuss the role of advanced imaging techniques, such asMR diffusion-weighted imaging (DWI), diffusion tensor im-aging, fluoro-2-deoxy-D-glucose positron emission tomogra-phy CT (FDG-PET CT), and positron emission tomographyMRI (MRI PET) as problem-solving tools in the evaluation ofthose orbital masses that present with non-specific morpho-logic imaging findings.Main messages/Teaching points• A compartment-based approach is essential for the diagno-sis of orbital tumours.

• CT and MRI play a key role in the work-up of orbitaltumours.

• DWI, PET CT, and MRI PET are complementary tools tosolve diagnostic dilemmas.

• Awareness of salient imaging pearls and diagnostic pitfallsavoids interpretation errors.

Keywords Orbit tumours . Magnetic resonance imaging(MRI) . Diffusionweighted imaging (DWI) . Positronemission tomographyCT (PETCT) . Positron emissiontomographyMRI (MRI PET)

AbbreviationsACC Adenoid cystic carcinomaADC Apparent diffusion coefficientBMT Benign mixed tumourCECT Contrast-enhanced CTCEMRI Contrast-enhanced MRIDTI Diffusion tensor imagingDWI Diffusion-weighted imagingFA Fractional anisotropyFD Fibrous dysplasiaFDG Fluoro-2-deoxy-D-glucosePET CT positron emission tomography CT

* Minerva [email protected]

1 Department of Radiology, Geneva University Hospital andUniversity of Geneva, RueGabrielle-Perret-Gentil 4, 1211, Geneva14, Switzerland

2 Department of Neuroradiology, Geneva University Hospital andUniversity of Geneva, RueGabrielle-Perret-Gentil 4, 1211, Geneva14, Switzerland

3 Department of Nuclear Medicine, Geneva University Hospital andUniversity of Geneva, RueGabrielle-Perret-Gentil 4, 1211, Geneva14, Switzerland

4 Department of Clinical Pathology, Geneva University Hospital andUniversity of Geneva, RueGabrielle-Perret-Gentil 4, 1211, Geneva14, Switzerland

Insights Imaging (2016) 7:43–68DOI 10.1007/s13244-015-0443-8

http://crossmark.crossref.org/dialog/?doi=10.1007/s13244-015-0443-8&domain=pdf

MRI PET positron emission tomography MRIFS Fat saturatedFT Full echo trainHR High resolutionH&E stain Haematoxylin-eosin stainIHC ImmunohistochemistryIgG4-RD Immunoglobulin G4-related diseaseIOP Inflammatory orbital pseudotumourMALT Mucosa associated lymphoid tissueNECT Non contrast-enhanced CTNF NeurofibromatosisNHL Non-Hodgkin’s lymphomaONG Optic nerve gliomaONSM Optic nerve sheath meningiomaOLPD Orbital lympoproliferative disordersOPNF Orbital plexiform neurofibromaRMS RhabomyosarcomaRT RadiotherapySCC Squamous cell carcinomaSUV Standardised uptake valueUS UltrasoundVLM Veno-lymphatic malformation

Introduction

The orbit is a small anatomical space with a wide range ofimportant structures within. Tumours and tumour-like lesionsoften arise from these orbital contents and are a common in-dication for the radiological evaluation of the orbit in bothadults and children. Cross-sectional imaging plays a vital rolein the diagnosis and management of these lesions. Knowledgeof the clinical presentation and patient’s age helps to limit thedifferential diagnosis and to determine the appropriate imag-ing modality. Certain orbital pathologies such as retinoblasto-ma and rhabdomyosarcoma (RMS) are typically found in chil-dren, whereas malignant uveal melanoma, lymphoma, andinflammatory orbital pseudotumour (IOP) are seen in adults.Clinical symptoms such as extraocular muscle palsies, diplo-pia, visual impairment, exophthalmos, and eye pain can serveas useful pointers to the likely pathology. However, a biopsymay be needed to provide tissue diagnosis [1–4].

The purpose of this review is to discuss the clinical, imag-ing, and histopathological features of commonly encounteredorbital tumours and tumour-like conditions. We highlight therole of cross-sectional imaging in the evaluation of indetermi-nate orbital masses with emphasis on advanced imaging tech-niques such as MR diffusion weighted imaging (DWI), diffu-sion tensor imaging (DTI), fluoro-2-deoxy-D-glucose (FDG)-positron emission tomography CT (PET CT), and positronemission tomography MRI (PET MRI or MRI PET, the Eu-ropean Congress of Radiology uses MRI PET as the abbrevi-ation to emphasize its imaging value). We discuss their impact

on the differential diagnosis of those lesions, where conven-tional morphologic cross-sectional imaging is non-specific.

Imaging techniques

Evaluation of suspected orbital masses can be done with mag-netic resonance imaging (MRI), computed tomography (CT),ultrasound (US), fluoro-2-deoxy-D-glucose positron emissiontomography/CT (FDG-PET CT), and, recently, MRI PET.Most investigators agree that MRI is the imaging modalityof choice, whereas CT should be reserved for cases withsuspected bony pathology and whenever MRI cannot be per-formed. As shown by several investigators, high resolutionMRI (HR MRI) shows superior soft tissue contrast than CTand allows more accurate depiction of the different orbitalcompartments [1–3]. MRI examinations can either be per-formed on a 1.5 T or on a 3 T scanner using a combinationof head and surface coils. The standard MRI protocol in mostinstitutions consists of axial SE T1W and TSE T2W se-quences, coronal STIR sequences, and axial and coronal SET1W sequences with fat saturation obtained after intravenousadministration of gadolinium chelates. The recommendedslice thickness is 2–3 mm with a 512×512 matrix. 3D FTheavily T2W sequences (CISS, FIESTA, or DRIVE) and3DFT T1W sequences with 0.6-1 mm thin slices (VIBE,THRIVE) after intravenous contrast material administrationare additionally used by some investigators including our-selves, as these volumetric data sets allow multiplanar recon-structions in any given plane, thereby facilitating the evalua-tion of subtle findings.

In patients with suspected orbital masses, CT is the modal-ity of choice for evaluating calcifications and osseous orbitallesions and in patients with possible metallic foreign bodies[1–3]. CT examinations are usually performed using 0.6–1 mm thin slices after intravenous injection of iodinated con-trast material. Thin-slice HR multidetector CT provides quickvolumetric acquisitions and precise depiction of the globe,optic nerve, intraconal, and extraconal spaces. Standard coro-nal and sagittal reconstructions are routinely obtained withbone and soft tissue settings.

Because of the superficial location of the globe and itscystic nature, ultrasound (US) with Doppler allows accuratedepiction of a variety of pathologic conditions of the globeand orbit, and enables non-invasive and cost-effective follow-up. The technique is well tolerated, easy to perform, and has ahigh accuracy for the characterization of vascular lesions inskilled hands.

Role of advanced imaging

In recent years, advanced imaging techniques such as DWI,DTI, FDG-PETCT, andMRI PETare being increasingly used

44 Insights Imaging (2016) 7:43–68

in the pre-therapeutic work-up and post-therapeutic monitor-ing of patients with head and neck tumours [5–15]. Thesemodalities are also making significant inroads in ophthalmo-logic imaging. The physiological and functional informationobtained by these techniques can be used to complement mor-phological findings obtained from conventional imaging,thereby aiding non-invasive tissue characterization [4, 8–23].AlthoughDWI sequences are widely used to assess primary orrecurrent head and neck tumours, their applications in the orbitare still limited in clinical routine due to geometric distortioncaused by the adjacent bone, air, and soft tissue interfaces.Nevertheless, the development of newer, robust single shotecho-planar DWI or multishot echo-planar DWI (such as theRESOLVE sequence) holds promise for the evaluation of or-bital tumours and optic nerve pathology. DWI produces con-trast on the basis of diffusivity of water molecules in differenttissues and can thus be a source of information for assessingpathological tissue. Echo-planar DWI can help to differentiatebetween benign and malignant orbital masses based on appar-ent diffusion coefficient (ADC) values. DWI is more useful incharacterizing infiltrative orbital masses, which appearhypointense on T2W images as compared to well-defined hy-perintense lesions. Malignant masses especially orbital lym-phomas show visually and quantitatively lower ADC valuesas compared to benign masses. Restricted diffusion is attrib-uted to the higher cellularity and higher nuclear: cytoplasmicratios in malignant lesions. Sepahdari et al have reported thatan ADC value of 1.0 – 1.15×10−3 mm2/s represents an opti-mal threshold for predicting malignancy with a reported sen-sitivity of 95 %, specificity of 91 % and accuracy of 93 % [9,10]. Visual assessment of benign and malignant lesions maynot reveal significant differences on just DW images becauseof the T2-shine through effect. However, ADC maps are onlyaffected by diffusivity changes. DWI can help to localize ma-lignant masses in a background of non-specific inflammationand guide biopsy or intervention [9–13].

DTI is a novel MRI technique, which allows anatomicmapping and quantitative characterization of white matter ar-chitecture by measuring molecular diffusion [24]. DTItractography is a computational procedure, which reconstructswhite matter tracts in 3D-space based on their anisotropy char-acteristics. Tractography is used to provide a roadmap for thepre-surgical assessment of white matter tracts involved bytumours. Advances in MR data acquisition and post-processing now permit high-resolution DTI of cranial nervesin a clinical setting. The antero-posterior orientation and fairlylarge size of the optic nerve and tracts provide favourableparameters for tractography. DTI can be used to map opticnerve fibres when involved by tumourous conditions such asgliomas or meningiomas. Depending on whether the tumourdisplaces or infiltrates the nerve fibres, appropriate function-saving nerve surgery can be planned [3, 14–16]. However,DTI images of the optic nerve may show severe geometric

distortion, in particular in the region of the orbital apex, andfibre tracking of the optic nerve is still part of ongoing clinicalresearch protocols.

FDG-PET CT has recently emerged as a problem-solvingtool in ophthalmologic oncology. It provides functional infor-mation regarding tumour metabolism based on FDG uptake.The level of FDG uptake depends upon tumour type andgrade, size, surrounding metabolic activity, and blood glucoselevels. For most primary orbital lesions, PET CT does notseem to provide any significant advantage over clinical eval-uation and CT/MR imaging, other than detecting distant andmetastatic lesions missed by conventional imaging. However,PET CT is now part of standard protocol in the initial stagingwork-up and post treatment assessment of orbital/ocular ad-nexal lymphomas. PET/CT also seems appropriate for meta-static tumours to the orbit and ocular adnexae from other pri-mary sites. In these cases, one single comprehensive studymay be preferable to performing multiple CT scans with con-trast. The potential pitfalls in FDG-PET CT imaging of theorbit include background physiological uptake in extra-ocularmuscles, poor uptake in very small lesions, and the likelihoodof missing subtle uptake due to being at the edge of the field ofview in standard skull to upper thigh PET CT scans [21].Comparing standardized uptake values (SUV) between malig-nant and benign lesions and lesion to surrounding tissue helpsin increasing diagnostic accuracy [17–21].

MRI PET leverages the superior soft-tissue contrast andfunctional sequences of MRI with the molecular informationof PET in a single hybrid imaging technique. MRI PET is stilla clinical research tool, however, recent publications haveshown that MRI PET has an equivalent performance withrespect to lesion detection as PET CT in the evaluation ofhead-neck cancers [7, 23]. Although large-scale data and stud-ies on the role of MRI PET in orbital conditions are stillawaited, it can be a considered as a potential future tool inrefining orbital imaging. Paediatric and pregnant patients maybenefit fromMRI PET because of reduced radiation burden ascompared to PET CT. MRI PET may play a valuable role inthe evaluation of paediatric lymphomas, neuroblastomas. andsoft tissue sarcomas [22, 23].

Compartment-based approach to orbital masses

The orbit can be anatomically divided into some well-definedcompartments (Fig. 1). The muscle cone comprising the fourrectus muscles divides the orbit into the intraconal andextraconal compartments. The intraconal compartment con-tains the globe, the optic nerve-sheath complex, orbital ves-sels. and nerves (Fig. 1). The extraconal compartment consistsof the bony orbital walls, fat. and the lacrimal gland. Theorbital septum and lid form the anterior or preseptal compart-ment. Localizing orbital lesions to these specific

Insights Imaging (2016) 7:43–68 45

compartments helps to simplify the diagnostic approach andnarrow down the list of differentials [1].

In this review, we will describe tumours of the globe andoptic nerve first, followed by the conal-intraconal tumours,extraconal tumours, and finally tumours of the bones/sinuses(Table 1). Examples of multi-compartmental masses will alsobe discussed (Table 1).

Globe

Retinoblastoma

Retinoblastoma is a malignant, primary retinal neoplasm andthe most common intraocular tumour of childhood. About90 % of cases occur under 5 years of age. Retinoblastoma

can occur in a hereditary form (40 %) or in a sporadic form(60 %). In both cases, patients have mutations of the retino-blastoma tumour suppressor gene on chromosome 13q14 [1,3, 4, 25, 26]. Hereditary retinoblastoma is associated withearly onset disease; screening ultrasound (US) and MRI havebeen recently recommended for the management of fetuses athigh risk of developing this tumour [27]. The higher incidenceof retinoblastoma seen in developing countries has been partlyattributed to the presence of human papilloma virus in tumourtissue [28]. About 50 % of cases present with leukocoria and40 % show bilateral disease. Although the initial diagnosis isbased on ophthalmoscopy and US, cross-sectional imaging ismandatory to assess disease extent and prognosis. Extra-ocular extension occurs in less than 10 % cases and portendspoor prognosis. When a pinealoblastoma is associated withbilateral retinoblastomas, the term trilateral retinoblastoma isapplied. Low-grade intra-ocular retinoblastomas are treatedwith chemotherapy while advanced tumours require enucle-ation and/or radiotherapy (RT) [1, 3, 4, 25, 26].

Retinoblastoma arises from precursor cells of the retinalneuroepithelium. Histologically, undifferentiated areas of thetumour show characteristic "small blue cells" with scant cyto-plasm and large hyperchromatic nuclei. Differentiated struc-tures called Flexner-Wintersteiner rosettes are commonlyseen. Because of rapid growth of the tumour, necrosis andcalcifications are common; these features account for the char-acteristic radiologic appearances on CT and MRI [25, 26].Non-contrast-enhanced CT (NECT) demonstrates intra-tumoural calcifications in about 90 % cases. Marked enhance-ment of the tumour is seen on contrast-enhanced CT (CECT).MRI of the orbits and brain is usually performed together todetermine extraocular and intracranial extension as well as torule out an associated pinealoblastoma. The tumour is slightlyhyperintense on T1W images, hypointense on T2W images,and shows marked post contrast enhancement on contrast-enhanced MRI (CEMRI) (Fig. 2) [1, 4, 25, 29]. AlthoughCT is superior in calcium detection, MRI may allow equallyaccurate identification of calcifications by revealing spots oflow signal intensity on very thin T2 TSE and T2* weightedsequences [30]. Retinoblastoma may exhibit variablehyperintensities on DWI resulting in varying values on ADCmaps, depending on cellularity and histology. De Graaf et alhave reported statistically significant differences in ADCvalues in viable enhancing tumour tissue (1.03×10 −3 mm 2/s) as compared to non-viable necrotic tissue (1.47×10 −3 mm2/s). Thus ADC values can be used for monitoring treatmentresponse in retinoblastoma [31].

Other diseases causing leukocoria can be differentiatedfrom retinoblastoma based on clinical presentation and imag-ing characteristics. Coat’s disease, persistent primary hyper-plastic vitreous and toxocariasis lack calcifications. Retinopa-thy of prematurity rarely shows calcifications, it may be bilat-eral and history of prematurity is usually elicited [4, 25, 26].

Fig. 1 Schematic illustration of the orbital contents and compartments.Axial and coronal view of the right orbit. Black asterisks indicate theintraconal compartment. Green asterisks indicate the extraconalcompartment


Unlike in adult cancers, the role of PET CT in paediatricpatients is still not widely established. As intraocular retino-blastomas may not be FDG avid, it appears that PET CT doesnot have a role in their evaluation. Nevertheless, it has beensuggested that increased optic nerve uptake on baseline PETCT may be a predictor of lower event free survival and loweroverall survival as compared to patients without optic nerveFDG uptake [32].

Malignant uveal melanoma

Malignant uveal melanoma is the most common primary in-traocular tumour in adults. The incidence is highest amongstCaucasians with peak incidence at 53 years. Malignant mela-noma arises from the choroid in 85 % of cases. The diagnosisis usually made on ophthalmoscopy and US; however, cross-sectional imaging is necessary in case of opaque lens or sig-nificant subretinal effusion. Poor prognostic factors includeage>60 years, large tumour size, anterior uveal location andheavy tumour pigmentation. Photocoagulation, radiotherapy(RT), and globe sparing surgery are treatment options forsmaller tumours while enucleation is necessary for larger

Fig. 2 3-year-old boy with right-sided retinoblastoma. a.Axial 3D T2Wimage of the orbits shows a well-circumscribed retinal mass (solid arrow),which appears very hypointense as compared to the surrounding brightvitreous. Associated retinal detachment/haemorrhage (dashed arrows) ap-pears moderately hypointense. c. Sagittal contrast-enhanced FS T1Wimage of the same patient shows avid tumour enhancement (arrow).The tumour is limited to the globe. No other lesions were seenintracranially

Tab

le1

Overviewof

orbitaltum

oursandtumour-lik

elesionsusingacompartmentb

ased

approach.A

sterisks

indicatepossible,how

ever,rarediseasemanifestatio

nsin

therespectiv

ecompartment

Intraconalandconalm

asses

Extraconalm

asses

Multi-compartment

masses

Globe

Opticnervesheath

complex

Musclecone

and

retrobulbarfat

Orbitalappendages

(lacrimalglandandsac)

Other

extraconal

structures,bones,and

sinuses

Eyelid

Retinoblastom

aOpticnerveglioma

Cavernous

hemangiom

aEpitheliallacrimalglandtumours

(benignmixed

tumour,adenoid

cysticcarcinom

a,adenocarcinoma,

undifferentiatedcarcinom

a)

Dermoid/epidermoid

Eyelid

tumours(squam

ouscell

carcinom

a,basalcell

carcinom

a,melanom

a,lymphom

a)

Vascularmalform

ations

Hem

angioblastom

aOpticnervesheath

meningoma

Pseudotumour

Lym

phom

a,leukem

iaRhabdom

yosarcom

aLym

phom

a

Uvealmelanom

aLy

mphom

a*,leukemia*

Schw

annoma*of

cranial

nerves

III,IV,V

ISarcoidosis

Schwannomaand

perineuralspread

V1andV2

Rhabdom

yosarcom

a

Chorioid

metastases

Pseudotumour

Fibrousdysplasia,osteom

a,metastases,myeloma

Plexiform

neurofibroma

Metastases

Pseudotumour

Ig-G

4relateddisease


tumours. Systemic metastases to the liver, lungs, and brain areoften the cause of mortality [18, 26, 33].

The current WHO classification of choroidal tumours con-sists of three histological types, i.e. mixed, epitheloid, andnecrotic melanomas. Spindle cell A tumours are now classi-fied as benign choroidal nevi. Themixed type includes spindleB and epitheloid cells. The prognosis of spindle cell tumoursis better as compared to mixed or purely epitheloid melano-mas. Metastatic potential is determined by maximum tumourdimensions, number of epithelioid cells, vascular patterns, andnucleolar size and activity [26, 33, 34].

NECT shows a well-circumscribed, hyperdense,mushroom-shaped tumour with a broad choroidal base. Cal-cification is rare. CECT and CEMRI show marked post con-trast enhancement (Fig. 3). The melanin content causes char-acteristic hyperintense signal on T1W and hypointense signalon T2WMR images. Thin-section MRI enables accurate pre-diction of the degree of melanomatous pigmentation based onquantitative evaluation of T1W images. More pronouncedpigmentation is associated with poorer prognosis. Fat-saturat-ed, high-resolution CEMRI is ideal for demonstrating smallenhancing tumours, associated retinal detachment as well asextraocular disease. Imaging differentials include choroidalhemangioma, choroidal detachment, and uveal metastases[33]. False positive or false negative assessments for ocularmelanoma and other ocular tumours may be caused by retinaldetachment and highly myopic patients. In highly myopicpatients, the globe can be elongated and the resulting chemicalshift artefact can lead to asymmetric thickening of the outline

of the globe mimicking the presence of a tumour while, on thecontrary, retinal detachment may mask small tumours. Erb-Eigner et al have reported that ocular melanomas showmarked restricted diffusion with a mean ADC value of0.891×10−3mm2/s. Also, the mean ADC of ocular melanomaappears to be statistically significant from the mean ADC ofretinal detachment [35] thereby facilitating diagnosis.

FDG-PET CT has the potential to provide substantial ben-efit in the surveillance of uveal melanomas. Reddy et al foundthat PET CTwas able to detect metabolic activity of choroidalmelanomas, especially T3 and larger lesions. A positive cor-relation was found between SUVand the size of the melano-ma. However, PET CT is unable to differentiate between smallmelanomas and suspicious choroidal nevi [36]. Whole bodyPET CT has been shown to play a valuable role in detectingregional and distant metastases from choroidal melanoma.Kurli et al have reported 100 % sensitivity and specificity ofPET CT in the identification of hepatic metastases of choroi-dal melanomas [37].

Optic nerve-sheath complex

Optic nerve glioma (ONG)

ONG is the most common primary optic nerve tumour. Thelow-grade form is commonly seen in children with 75 % ofcases presenting before the age of 10 years. The less commonaggressive form is seen in adults and is often fatal. About 38%of paediatric patients with ONG have neurofibromatosis (NF)-1, and about 50 % of patients with NF1 harbour ONG. Bilat-eral disease is pathognomonic of NF-1 (Fig. 4). Most paedi-atric ONG cases involve the intraorbital and intracranial por-tions of the optic nerve; about 20 % may extend up to thechiasm, hypothalamus, and optic tracts. Involvement of thechiasm is common in adult ONG. Patients typically presentwith decreased vision and painless proptosis. Hypothalamiclesions can cause hydrocephalus. BenignONG are slow grow-ing tumours that do not metastasize. Imaging is mandatory toguide management and to document disease progression. Therole of chemotherapy and radiotherapy (RT) in the treatment isstill controversial. Long-term prognosis is excellent if the tu-mour is confined to the optic nerve; however, intracranialextension is associated with poorer survival rates [1, 4, 8,25, 26].

Most ONG are low-grade pilocytic astrocytomas (WHOgrade1). Histologically, these tumours are biphasic and consistof bipolar cells and multipolar cells. Bipolar cells showpilocytic processes, whereas multipolar cells may show eosin-ophilic granular bodies. In addition, Rosenthal fibres,microcysts, and neovascularity are commonly seen. Adultforms are usually aggressive anaplastic astrocytoma (WHOgrade 3) or glioblastoma multiforme (WHO grade 4) [25, 26].

Fig. 3 50-year-old male patient diagnosed with a left-sided uvealmelanoma on ophthalmoscopy. a. Axial contrast-enhanced CT imageshows a tiny, avidly enhancing nodule (arrow) along the choroid


On CT and MRI, ONG show fusiform or tubular enlarge-ment often with kinking of the optic nerve and ectasia of theoptic sheath (Fig. 4). Calcification is rare. Widening of theoptic canal and cystic degeneration may be seen. ONG areusually hypointense on T1W images, slightly hyperintenseon T2W images and show variable enhancement (Fig. 4).MRI is the imaging modality of choice as it detects smalltumours and elegantly maps out intraorbital as well as intra-cranial extensions. ONG can be differentiated from opticnerve sheath meningioma (ONSM) as the latter are commonerin adults, dark on T2W images, surround the optic nerve, andshow avid post-contrast enhancement [1, 4, 8, 25, 26].

ONG show increased diffusion on DWI; they exhibit highADC and low fractional anisotropy (FA) values. This is attrib-uted to their low cellularity and low proliferative indices [11,13, 38, 39]. Jost et al have reported on the use of DWI anddynamic contrast-enhanced imaging to calculate the diffusiv-ity and permeability of ONG. Similar to other pilocytic astro-cytomas, ONG showADC values in the range of 1.2-2.09×10-3 mm2/s. ADC values cannot distinguish between clinicallystable and clinically aggressive ONG. On the other hand, clin-ically aggressive ONG are seen to show significantly higherpermeability values than clinically stable tumours [38]. DTItractography can be used in the presurgical evaluation of ONGby demonstrating integrity of the optic nerve in patients withresectable lesions. Tractography can demonstrate divergence

or disruption of nerve fibres. This allows for minimal post-surgical morbidity and minimal vision loss [14–16, 39]. Fillipiet al found that DTI may offer increased sensitivity over con-ventional imaging in evaluating the optic pathways in NF-1patients. These patients showed statistically significant de-crease in FA values and elevated mean diffusivity values ascompared to age-matched controls [40]. Currently, no reliablefactors have yet been identified to predict future vision loss inpatients with ONG. Nevertheless, de Blank et al found thatdecreased FA of the optic radiations in patients with ONGwaspredictive of visual acuity loss during the following year and,therefore, suggested that DTI may be used as a non-invasivetool to prospectively identify those patients who will requiretherapy [41].

Although PET CT is not used routinely for paediatric pa-tients, Miyamoto et al have reported very high FDG uptake inan adult patient with ONG, which turned out to be an anaplasticastrocytoma on histology. They also reported an adult patientwith fibrillary astrocytoma of the optic nerve showing isointenseFDG uptake. Thus, PET CT may potentially play a role in thehistological grading of ONG, especially in adult patients [19].

Optic nerve sheath meningioma (ONSM)

ONSM is the most common primary tumour arising from theoptic nerve sheath. It is a benign, slow-growing tumour, which

Fig. 4 5-year-old boy with NF-I. a. Axial T2W MR image of the orbitsshows bilateral ONG (dashed arrows) causing fusiform enlargement andkinking of the optic nerves. A focal T2- hyperintense lesion (arrowhead)is seen in the right mesial temporal lobe. b. Coronal T2WMR image ofthe same patient shows extension of the bilateral ONG along theintracranial segments of the optic nerves (arrows). c. Axial contrast-

enhanced FS TIW MR image of the same patient shows prominentenhancement in the intracanalicular and intracranial segments ofbilateral ONG (arrows). There is also avid enhancement in thesuprasellar/chiasmatic region (arrowhead) and in the right mesialtemporal lesion (arrowhead) in keeping with tumour extension alongthe optic chiasm and right optic radiation


accounts for 5 % of primary orbital tumours and 2 % of allmeningiomas. It commonly occurs in females between 30-70years of age. Hormonal factors, radiation exposure, and he-reditary predisposition (abnormalities of chromosome 22)have been implicated in the aetiology. It is rare in childrenexcept in cases of neurofibromatosis (NF)-2. Primary ONSMarise from the intraorbital and intracanalicular segments of theoptic nerve while secondary ONSM are intraorbital extensionsof intracranial tumours. A primary ONSM may extend intra-cranially to involve the contralateral optic nerve. ONSM typ-ically presents with slowly progressive painless loss of vision(with preservation of central visual field) and progressiveproptosis. Although benign, these tumours have a tendencyto recur. Because of their slow progression, small ONSM areoften managed just by conservative follow-up imaging. Frac-tionated stereotactic RT is the treatment of choice for patientswith preservable vision [1, 8].

ONSM arises from the arachnoid cap cells within the opticnerve sheath. Histologically, an ONSM reveals various sub-types of which the meningothelial (lobules of tumour cells),fibrous (bundles of spindle cells), and transitional types(whorls, psammoma bodies) are most common. All these areWHO grade 1 benign tumours. In benign meningiomas, tu-mour cells are uniform, mitoses are rare and necrosis is absent.Atypical meningiomas (WHO grade 2) have increased mitoticactivity and cellularity, prominent nucleoli, and necrosis;some are of clear cell subtype. Anaplastic meningiomas(WHO grade 3) include rhabdoid/papillary subtypes and his-tological features of frank malignancy like extensive mitosesand necrosis [26, 42].

The diagnosis of ONSM depends on cross-sectional imag-ing. NECT commonly shows tubular thickening and calcifi-cation of the optic nerve sheath complex. An enlarged opticnerve canal and hyperostosis may be seen. Although MRI isless sensitive than CT for detection of calcifications, it is idealfor assessing the intracanalicular and intracranial extension ofONSM. ONSM demonstrates similar intensity as the opticnerve on T1W and T2W images. Fat-saturated, thin-sectionCEMRI images show a tubular enhancing mass around theisointense optic nerve (tram track sign on axial images/targetsign on coronal images) (Fig. 5). ONG is the closest imagingdifferential; however, ONG is more common in children, doesnot calcify, expands the optic nerve, often associated withother stigmata of NF-1, and may extend intracranially alongthe optic pathways [1, 8]. Abnormal enhancement of the opticnerve sheath causing the tram track sign or the target signappearance on cross-sectional imaging may also be seen inthe setting of lymphoma, leukemia, and inflammatorypseudotumour or can be caused by tumour seeding into thesubarachnoid space (as the optic nerve sheath communicateswith the intracranial subarachnoid space).

Because of its hypercellular nature, ONSM often showsrestricted diffusion with low ADC values on DWI [9–12]

(Fig. 5). Sepahdari et al have reported ADC values in therange of 0.79-1.04×10−3 mm2/s for ONSM [9]. Zang et alhave illustrated a case of tractography demonstrating opticnerve displacement and atrophy due to an invasive orbitalmeningioma [15].

It has been reported that WHO grades 2 and 3 dural me-ningiomas show higher FDG uptake than grade 1 tumours.Thus, FDG uptake correlates with the proliferative activityof meningiomas [43, 44].

Conal-intraconal compartment

Cavernous hemangioma

Cavernous hemangioma is the most common benign orbitaltumour-like condition in adults. According to the classifica-tion of vascular malformations by the International Society forthe Study of Vascular Anomalies (ISSVA), cavernous heman-gioma is a venous or low flow malformation [1–4, 8]. It ismore common in women and usually seen in the 2nd–4thdecades. It is typically intraconal and presents with slowlyprogressive, unilateral proptosis, and/or diplopia. Occasional-ly, compression of the optic nerve may result in mild visualdeficit. Unlike childhood capillary hemagiomas, cavernoushemangiomas do not show cellular proliferation nor do theyhave a prominent arterial supply. In fact, they are isolated fromthe orbital vascular system. Asymptomatic tumours are usual-ly observed conservatively. Surgical resection is performed tocorrect visual disturbance and cosmetic problems. Visualprognosis is excellent in most cases [1, 2, 45, 46].

Histologically, cavernous hemangiomas consist of largeblood-filled spaces lined by flattened endothelial cells andseparated by scant fibrous tissue. Stagnant circulation mayresult in venous thrombosis. Dystrophic calcification is com-mon [26, 45]. Cavernous hemangiomas can coexist with othervascular malformations of the orbit like venous varix andlymphangioma [47].

On NECT, a cavernous hemangioma is seen as a well-circumscribed, dense intraconal mass. It is usually seen sepa-rately from the optic nerve and extraocular muscles CECTmay show patchy or uniform enhancement (Fig. 6).Phleboliths, if present, help to confirm the diagnosis (Fig. 6).On MRI, the lesion typically appears iso- to hypointense onT1W images and hyperintense on T2W images, althoughsome hemangiomas may display moderately high/low signalintensity. Some scattered hyperintense areas on T1W imagesmay indicate thrombosis. Fat-suppressed, dynamic CEMRIshows initial patchy enhancement followed by homogeneousenhancement in the delayed phase (Fig. 7). Imaging differen-tials include venous varix and, less often, schwannoma. Avenous varix shows intermittent intralesional flow and exoph-thalmos on Valsalva manoeuvre [1, 2, 45, 46]. Schwannomasalso appear well-circumscribed, iso-hypointense on T1W


Fig. 5 41-year-old woman with right-sided progressive vision loss andproptosis. a. Axial T2W image shows a moderately hpointense fusiformlesion originating from the optic nerve sheath encasing the optic nerve(arrow). b. Corresponding axial ADC map from RESOLVE DWI showsrestricted diffusion (arrow). Note only minor image deformation. c. ADCmap from standard EPI sequence also shows restricted lesion diffusivity(arrow); however, note major image deformation due to susceptibilityartefacts. d. Axial contrast enhanced T1W image reveals strong fusiform

enhancement along the optic nerve (Btram track sign^, arrow). There wasno extension through the orbital apex intracranially. e. Coronal fat satu-rated T1W image displaying concentric enhancement of the tumouraround the compressed optic nerve creating a characteristic Bbull’s eye^appearance (arrow). Imaging findings are in keeping with an ONSM. f.DTI 3D tractography reconstruction of the optic nerves reveals normalfibres on the left (fibers are depicted in green due to their anterior- poste-rior course) and major fibre atrophy on the right (arrow)

Fig. 6 Orbital hemangioma asseen on CT in two differentpatients. a. Coronal NECT in a30-year-old male patient shows awell-circumscribed intraconalmass (arrow) with calcifiedphleboliths. b-d. 50-year-oldmale patient with an incidentallydiagnosed left orbital cavernoushemangioma on an angio-CTperformed for stroke. b. NCECTshows a nonspecific intraconallesion (arrow) withoutphleboliths. Arterial phase (c)demonstrates initial patchyenhancement (arrow) followed byprogressive filling of the lesion inthe venous phase (d)


images, and hyperintense on T2W images. However, thespread pattern on dynamic CEMRI can help to distinguishbetween schwannoma and cavernous hemangioma. In the ear-ly phase, enhancement in hemangiomas starts at one point,whereas it starts from a wide area in schwannomas [48, 49].

Cavernous hemangiomas appear bright on DW imageswith mean ADC values ranging from 1.23×10−3 mm2/s to1.39×10−3 mm2/s [9, 10, 12] (Fig. 7). Razek et al have report-ed that schwannomas have mean ADC value of 1.92×10−3

mm2/s, which is statistically different from that of cavernoushemangiomas [12].

Scinitigraphy using technetium 99 m-labelled redblood cells can help in the differential diagnosis of cav-ernous hemangioma from other imaging mimics [50].Miyamoto et al have described two cases of adult orbitalcavernous hemangiomas showing isointense FDG uptakeon PET/CT [19].

Extraconal compartment

Dermoid

Dermoids are the most common congenital orbital lesions,accounting for about 25 % of all orbital biopsies. They arisefrom epithelial sequestration, usually at the zygomaticofrontaland frontoethmoidal sutures. They are typically seen in theextraconal region, superolaterally, between the globe and the

orbital periosteum. They are slow growing lesions; however,they may occasionally rupture and mimic acute inflammation.Small dermoids do not require immediate treatment and areusually removed within the 2nd or 3rd year of life. Completeexcision without rupturing is necessary in order to avoid in-flammatory reactions or local recurrences [1, 26, 51].

Macroscopically, orbital dermoids are round or oval-shaped, encapsulated tumours, containing various skin ap-pendages and fatty material. Histologically, a dermoid is linedby squamous epithelium and may contain hair follicles, seba-ceous glands as well as keratinous debris [26, 51].

In addition to clinical examination, which is sufficient formost superficial dermoids, US scans help to demonstrate asharply outlined lesion with a capsule and low-reflectivitycontents. CTor MRI are rarely necessary. NECTshows a wellcircumscribed, cystic tumour of low or fat density. Fat-fluidlevels and calcifications may be seen. Bony scalloping of thelacrimal fossa may occur due to pressure effect. On MRI,dermoids typically appear hyperintense on T1W and T2Wand hypointense on STIR (Fig. 8). Rim enhancement is rare[1, 26, 51]. Diffusion in dermoids may be variable dependingupon their contents. Lope et al and Sepahdari et al have de-scribed restricted diffusion in orbital dermoids [9, 13], where-as Razek et al have described ADC values in the range of1.68-1.95×10−3 mm2/s for head-neck dermoids [52]. Mostoften, the detection of macroscopic fat in dermoids is diagnos-tic and DWI adds no additional value (Fig. 8).

Fig. 7 60-year-oldmanwith left orbital cavernous hemangioma. CoronalSTIR image (a) shows a well-circumscribed hyperintense intraconal mass(arrow) causing superior displacement of the left optic nerve (thin arrow).b. ADC map shows moderately hypointense signal within the mass withan ADC value of 1.4×10 −3 mm2/s. c. Axial contrast-enhanced TIW

image shows initial patchy enhancement. d. Sagittal reformatted imagefrom a contrast-enhanced 3D VIBE acquisition obtained after the T1Wsequence shows characteristic progressive filling (arrow). Major masseffect on the optic nerve (thin arrow). The patient underwent surgery,which confirmed the diagnosis of cavernous hemangioma


Cephalocoeles can occur in the fronto-orbital region nearthe midline and can mimic dermoids. Cephalocoeles show atrack leading to the anterior cranial fossa, contain cerebrospi-nal fluid and show no fat content [51].

Lacrimal gland tumours

Lacrimal gland tumours are classified as epithelial andnon-epithelial lesions. Lacrimal gland epithelial tumoursare similar to salivary gland tumours and constitute 40–50 % of all lacrimal masses. Half of these are benignmixed tumours (BMT), while the other half are malignantmasses. Adenoid cystic carcinoma (ACC) is the mostcommon lacrimal gland malignancy, followed by carcino-ma ex-pleomorphic adenoma, adenocarcinoma, andmucoepidermoid carcinoma. Lymphoma, inflammatoryconditions, and non-carcinomatous metastases constitutethe non-epithelial lesions.

Benign mixed tumour (BMT)

BMT or pleomorphic adenoma originates mainly from theorbital lobe of the lacrimal gland. It is seen in middle-aged patients (40-50 years) without gender predilection.

Clinical signs include a painless, slow-growing mass inthe lateral orbit, usually persisting for more than12 months. Proptosis may be seen. Although benign,these tumours can show recurrence and malignant trans-formation (carcinoma ex-pleomorphic adenoma), primari-ly in cases where only a biopsy or incomplete excisionwere performed. Hence, meticulous surgical excision andcareful pathological examination for capsular invasion ismandatory [53, 54].

BMT arise from the ductal system of the gland. Theseencapsulated tumours contain interspersed epithelial andstromal components. Necrosis, hyalinization, myxoid, andmucinous degeneration may be seen [26, 53, 54]. Pseudo-podia and satellite tumours have been described histolog-ically in more than 50 % of BMT arising in the parotidgland, these histological features being associated with ahigher risk of recurrence [55]. Pseudopodia, satellite le-sions, and bony remodelling can equally be seen in BMTsarising in the lacrimal glands; they should not bemisinterpreted as a feature of malignancy (Fig. 9). OnCT, BMT are seen as well-circumscribed, round-ovalmasses with varying attenuation depending upon theircomposition and cellularity. Highly cellular masses appearhomogeneous. Cystic degeneration may give rise to

Fig. 8 42-year-old male with a histologically proven right orbitaldermoid. Coronal T1W (a), axial T2W (b), axial T1W (c), axial ADCmap (d), and coronal FS contrast-enhanced T1W (e) images show anorbital lesion with an anterior component containing fatty tissue (thickwhite arrows) and a posterior component containing non-fatty elements(hollow arrows). There are some fluid droplets in the anterior component(thin arrows). Note minor capsular enhancement after gadolinium

administration. The ADC values are very low in the anterior part of thelesion (ADC=0.1×10 −3 mm2/s) due to fat and they are very high in theposterior component (ADC=1.8×10 −3 mm2/s) due to fluid. f. DTI 3Dtractography reconstruction of the optic nerves (green) viewed fromabove and from the left. Right optic nerve fibres (white thin arrows)and left optic nerve fibres (green thin arrows) are normal and have similarFA and ADC values. Thick arrow points to the dermoid


hypodense/inhomogeneous appearance. Lacrimal fossadeformation and calcifications may be seen on bone-window CT. On MRI, a heterogeneous signal is identified,especially on T2W images with moderate/heterogeneousor homogenous contrast enhancement (Fig. 9). Infiltrationof the adjacent orbital tissue and poorly defined marginssuggest malignant transformation [53, 54]. Motoori et alproposed that the detection of myxomatous tissue onT2W, inversion recovery, DWI, and dynamic contrast-enhanced sequences help to differentiate BMT from othermalignant tumours [56].

Similar to salivary gland BMT, lacrimal gland BMT do notshow restricted diffusion (Fig. 9) [56–58]. Sepahdari et al havereported a single BMT of the lacrimal gland with ADC valueof 1.37×10 −3 mm 2/s [9], Razek et al have reported ADCranges in BMT between 1.62-1.76×10 −3 mm2/s [12], where-as Elkhamary et al have reported ADC ranges between 1.18-1.23×10 −3 mm2 /s [58]. These ADC values are significantlyhigher than the malignancy threshold value of 1.0×10−3 mm2/s [9, 10, 12, 56–58]. Thus, ADC values appear to be highlysensitive and specific in differentiating BMT from malignanttumours of the lacrimal gland.

Malignant epithelial lacrimal gland tumours

Approximately 50 % of epithelial lacrimal gland tumoursare malignant. Malignant tumours of epithelial origin in-clude adenoid cystic carcinoma (ACC), mucoepidermoidcarcinoma, adenocarcinoma, squamous cell carcinoma,and undifferentiated carcinoma types, such as the mammaryanalog secretory carcinoma of salivary origin (Fig. 10).Overall, these tumours are quite rare, accounting for lessthan 5 % of all lacrimal gland lesions. Nevertheless, malig-nant lacrimal gland tumours need to be recognized at anearly stage, as they tend to have a high morbidity and mor-tality. ACC is a high-grade malignancy accounting for 29 %of all epithelial lacrimal gland tumours and as many as 50 %of all malignant epithelial lacrimal gland neoplasms. Its in-cidence peaks in the 4th decade. Patients present with a hardmass in the upper lateral orbit, often with pain caused byperineural spread or bony invasion. Perineural spread indi-cates poorer prognosis. Radical resection with wide marginsis performed for small, low-grade tumours. Survival ratesvary from 5 years in 40 % of patients to 15 years in 58 % ofpatients [1, 2, 53, 54]. Histologically, these tumours are

Fig. 9 42-year-old female patient with BMTof the left lacrimal gland. a.Axial T2WMR image shows a well-circumscribed polypoid mass (thickarrow) ofmoderately hypointense signal involving the left lacrimal gland.Note small satellite nodules (thin arrows). b. Corresponding T1W imageshows non-specific lesion hypointensity (arrow). c. ADC map revealsincreased diffusion (ADC=1.6×10 −3 mm2/s). d. Coronal contrast-enhanced FS T1W MR image of the same patient demonstrates strongenhancement within the mass (thick arrow) and within the peripheralnodules (thin arrows). e. Sagittal reformatted 0.6 mm thin image from

contrast-enhanced 3DVIBE better illustrates scalloping of the orbital roofby the peripheral Bgrape-like^ nodules (thin arrows). e. Photomicrographof the surgical specimen (original magnification 100x, H&E stain)illustrates the characteristic histological features of pleomorphicadenoma with medium sized cells with an eosinophilic cytoplasm andmyoepithelial cells (small asterisk) partly surrounded by a myxoid matrix(large asterisk). The peripheral nodules seen on MRI correspondedhistologically to pseudopodia and satellite nodules. Bony invasion bypseudopodia was confirmed histologically


characterized by absence of a mesenchymal matrix. Theyshow different histological types like tubular, comedo-car-cinoma, basaloid, or cribriform patterns. The cribriform pat-tern consists of sheets of basaloid epithelial cells and sur-rounding spaces of varying shapes giving rise to a charac-teristic Swiss cheese appearance [26, 53, 54].

CT shows non-specific findings; often a well or poorlycircumscribed mass involving the lacrimal gland with associ-ated bony destruction in 70 % cases (Fig. 11). Low-gradetumours may exactly mimic BMT with a well-circumscribedmargin and no bony destruction. Intratumoural calcificationsare more common in ACC, in adenocarcinoma and in undif-ferentiated epithelial tumours (Fig. 10) than in a BMT andshould not be misinterpreted as phleboliths. ACC often ap-pears hypointense on T1W images, hypo- or hyperintense onT2W images and shows prominent post-contrast enhancement(Fig. 11). Fat-saturated CEMRI is ideal for local tumour stag-ing and for evaluating perineural spread [1, 2, 53, 54]. Ingeneral, most ACC will show perineural spread at microscop-ic examination; however, radiologically, perineural spreadmay remain undetected unless involvement of major nervetrunks, such as where the supraorbital nerve occurs (Fig. 11).

Elkhamary SM et al have reported 0.8×10 −3 mm2 /s as themean ADC value for ACC (which is significantly lower thanBMT and other benign lesions), but significantly higher than

lymphomas (0.6×10 −3 mm2/s) [58]. ADC values can help todifferentiate between carcinomas, lymphomas, metastases,and inflammatory disorders (described in subsequent sections)[1, 9–12, 53, 54, 58]. Nevertheless, ACC is often indistin-guishable from other malignant epithelial tumours of the lac-rimal gland on MRI with DWI (Fig. 10) unless perineuralspread, which is more common in ACC, is detected(Fig. 11). Occasionally, mucoepidermoid carcinomas mayshow high T1 signal due to their mucin content.

ACC is commonly hypermetabolic on PET CT. Baek et alhave reported that PET CT was successful in detecting boththe primary lesion and distant metastases of lacrimal glandACC [17–19, 59].

Rhabdomyosarcoma (RMS)

RMS is the most common malignant mesenchymal tumour ofchildhood. The orbit is the most common location in the head-neck with 40 % of tumours appearing there. The incidencepeaks between 5-10 years of age, as shown by positron emis-sion tomography, with a slight predilection for boys. RMStypically arises in the extraconal compartment; however,intraconal extension is known. It presents with rapidly pro-gressive proptosis, ptosis, or signs of inflammation oftenprompting urgent imaging. It is an aggressive tumour and

Fig. 10 65-year-old male patient with undifferentiated ductal carcinomaof the right lacrimal gland (mammary analog secretory type). a. AxialNECT of the orbits shows a well-circumscribed, hyperdense mass withstippled calcifications involving the right lacrimal gland. Thecalcifications were misdiagnosed as phleboliths, which led to the initialdiagnosis of a cavernous hemangioma. b. Axial T2W MR image of thesame patient shows that the lacrimal gland mass has a very hypointenseposterior component (thick arrow) and an anterior moderatelyhypointense portion (thin arrow). c. Corresponding axial T1W MR

image shows that the mass is isointense to the rectus muscles. d. ADCmap reveals restricted diffusion (ADC=0.9×10 −3 mm2/s), suggesting amalignant tumour. e. Coronal FS contrast-enhanced T1 W image showsmoderate tumour enhancement and lobular appearance. f .Photomicrograph (original magnification 100x, H&E stain) shows ahighly cellular tumour with atypical nuclei and mitoses and areas ofnecrosis (asterisk). There were numerous areas of microscopicperineural spread and lymphatic invasion not detected by imaging


commonly infiltrates into the adjacent sinuses, orbital fissures,cavernous sinus, and middle cranial fossa. Hematogenousspread can occur to the lungs. Surgery and chemotherapy usedin combination may achieve good survival rates. RT isavoided because of the potential risk of cataract, encephalop-athy, and radiation-induced sarcomas [1, 2, 4, 26, 60].

RMS is believed to arise from primitive mesenchymal cells.RMS can be divided histopathologically into embryonal, pleo-morphic, alveolar, and botryoid subtypes. The alveolar subtypeis the most anaplastic variant characterized by tumour cellsspreading along soft-tissue septa. The rhabdomyoblast is thediagnostic cell in all types which shows granular eosinophiliccytoplasm with thick and thin filaments. Conventional H&Estaining is complimented with immunohistochemistry to detectmyoglobin and desmin which support the diagnosis [26, 60].

CT and MR are often used in combination to assesstumour size, extraorbital extension, bony destruction andintracranial involvement. RMS appears isodense to mus-cle on NECT and usually shows significant enhancementon CECT. It appears iso-intense to muscle on T1W im-ages, hypo or hyperintense on T2W images and showsmarked enhancement on CEMRI (Fig. 12). Necrosis andcalcification is uncommon [1, 2, 4, 26, 60].

Many benign and malignant entities may mimic the imag-ing features of RMS; however, the presence of unilateral, rap-idly progressive proptosis in a child must always raise concernfor RMS. Orbital cellulitis may show similar clinical features.On imaging, both conditions may show an orbital mass withadjacent paranasal sinus involvement. Fever, leukocytosis,and orbital fat stranding/abscess formation suggest infection.Although capillary hemangiomas manifest in a younger age-group (12-18 months), they may mimic a very vascular RMS.Capillary hemangiomas often show multiple flow-voids, avidcontrast enhancement, and high flow on time-resolved MRangiography. Associated cutaneous hemangiomas are seen inone third of cases. In cases with equivocal clinical and imag-ing findings, a biopsy is necessary to reach the diagnosis.Langerhans cell histiocytosis may present with orbital in-volvement in 23 % cases. It can appear as an aggressive softtissue mass with bony invasion, similar to RMS. It may beassociated with diabetes insipidus. Again, a biopsy may benecessary to differentiate between the two. Neuroblastomametastases to the orbit can mimic RMS on imaging. The find-ing of a primary tumour in the retroperitoneum or posteriormediastinum helps to arrive at the correct diagnosis [60].Lymphoma is rare in children accounting for less than 5-

Fig. 11 50-year-old male patient with histologically proven ACC of theleft lacrimal gland. Axial NECTof the orbits shows a well-circumscribed,slightly hyperdense mass (arrow) involving the left lacrimal gland. Thereis suggestion of minimal adjacent bony scalloping. b. Coronal contrast-enhanced FS TIW image of the same patient shows avid, homogeneous,contrast enhancement within the mass (asterisk), mimicking a cavernoushemangioma. There is thinning of the overlying left frontal bone (arrow).c. Axial T2W image of the same patient showing intermediate signal

within the mass (asterisk) suggesting high cellularity, a feature that isuncommon in hemangioma. The patient underwent surgery, whichrevealed ACC with multiple areas of microscopic perineural spread notdetected by imaging. d. Contrast-enhanced axial T1W image obtained ina different patient 10 years after surgery of an ACC of the left lacrimalgland shows macroscopic perineural tumour recurrence along thesupraorbital nerve (arrows). The findings were confirmed histologically


10 % of orbital lesions. Unlike RMS, it commonly involvesthe lacrimal gland, appears hypointense on T2W images, en-cases rather than distorts the globe and shows even lowerADC values than RMS [4, 13, 60] .

Sepahdari et al have reported 0.72×10 −3 mm2/s as themean ADC value in a cohort of 12 cases of orbital RMS[10] (Fig. 12). Lope et al have stated that the low ADC valuesof RMS can help to differentiate them from haemangiomaswhich usually show high ADC values [13]. Hassold et al havereported a case of orbital RMS where low ADC value withinthe recurrent tumour (0.62×10 −3 mm2/s) helped to differen-tiate it from post-therapeutic changes [61].

PET CT is a valuable adjunct for the grading and staging ofpaediatric sarcomas [62]. FDG uptake is known to correlatewith the tumour grade of mesenchymal sarcomas [62, 63](Fig. 12). PET CT has been deemed superior at detectingosseous and nodal metastases of RMS than conventional im-aging [62, 64]. Whole-body MRI has shown comparable re-sults as PET CT, and more accuracy as compared to skeletalscintigraphy in the detection of osseous metastases of RMS[65]. MRI PET may potentially improve the staging, follow-up and post-treatment assessment of RMS [22].

Lymphoma

Lymphoma of the ocular adnexa is the most common orbitalmalignancy accounting for 55 % of adult malignant orbital

tumours. This is a heterogeneous group of tumours composingapproximately 1-2 % of non-Hodgkin’s lymphomas (NHL)and 8 % of extranodal mucosa-associated lymphoid tissue(MALT) lymphomas. Highest incidence is seen in the 6th–7th decade. Lymphoma can be primary to the orbit or second-ary to systemic disease. Secondary ocular involvement occursin 2-5 % of patients with advanced systemic NHL. About75 % of patients with primary orbital lymphoma eventuallydevelop systemic disease. Patients with Sjögren’s syndromehave a higher risk of developing extranodal NHL as comparedto age-, race-, and sex-matched controls. Sjögren’s syndrome,either primary or secondary (due to rheumatoid arthritis, sys-temic lupus erythematosus, or progressive systemic sclerosis),is an autoimmune disease of the exocrine glands characterizedby lymphocytic infiltration of the affected glands. About 6 %of patients with Sjögren’s syndrome show clinically evidentNHL manifestations. Most NHL seen in patients withSjögren’s syndrome are of B cell lineage and can occur inthe salivary glands, lacrimal glands, lymph nodes, lung, andthyroid. In the orbit, NHL can be unilateral or bilateral. In theorbit, the anterior extraconal space and lacrimal gland are mostcommonly involved. Involvement of the lacrimal gland isseen in about 7 % of all NHL cases associated with Sjögren’ssyndrome and manifests clinically with lacrimal gland en-largement. Other clinical manifestations of orbital lymphomainclude painless proptosis and motility disturbances. Whole-body staging is necessary when orbital lymphoma is

Fig. 12 4-year-old girl with a leftorbital RMS. a. Axial T2W MRimage of the orbits shows a conal-extraconal polypoid mass ofmoderately low signal intensitylocated superior to the left globe.b. ADC map shows restricteddiffusion (ADC=1×10 −3 mm2/s), suggestive of malignancy. c.Coronal contrast-enhanced FST1W MR image shows avidenhancement within the lesion. d.Axial FDG PET/CT image of thesame patient shows high SUVs(SUVmean=6, SUVmax=9).Although the lesion may mimic acavernous hemangioma on theT1W and T2W images, the lowADC and the high FDG uptakestrongly suggest a malignanttumour. Histology revealedembryonal rhabdomyosarcoma


diagnosed and is most often done with FDG PET CT. Low-grade tumours respond well to RTwhile chemotherapy is nec-essary for high-grade or systemic disease [1, 4, 18, 66, 67].

Histologically, ocular adnexal MALT lymphomas are char-acterized by a heterogeneous cell population, consisting ofmonocytoid, plasmacytoid, and centrocyte-like cells, with oc-casional blasts in the marginal zone surrounding lymphoidfollicles. Pathognomonic histological features include “follic-ular colonization” and the formation of “lymphoepithelial le-sions” through the invasion of neighbouring epithelial struc-t u r e s b y n e s t s o f MALT l ym p h om a c e l l s .Immunophenotypically, orbital MALT lymphomas showdense CD 20+, CD 10−and CD 23− B-cell lymphocytic infil-trates which helps to differentiate them from benign lympho-proliferative disorders and other small B-cell lymphomas.MALT lymphomas are typically negative for CD5, whichhelps to differentiate them from mantle-cell lymphomas [26,67].

NECT typically shows a hyperdense mass involving thelacrimal gland. The tumour usually molds to encase

surrounding orbital structures. Significant enhancement maybe seen on CECT. Bony destruction or perineural spread sug-gests an aggressive histology. High-cellularity tumours appearmoderately hypointense on T1W and T2W MR images(Figs. 13 and 14). CEMRI usually shows avid enhancement(Fig. 14). At times, isolated involvement of the extraocularmuscles or diffuse ill-defined orbital infiltration may be seen(Fig. 14) [1, 4, 66, 67].

Other infiltrative T2 moderately hypointense lesions name-ly benign orbital lympoproliferative disorders (OLPD), in-flammatory orbital pseudotumour (IOP), and granulomatousdiseases such as sarcoidosis and metastases (described subse-quently) are common imaging differentials [1, 9, 68, 69].

Orbital lymphomas typically show very low ADC values,usually between 0.44-0.92×10 −3 mm2/s (Figs. 13 and 14).Studies have proven that orbital lymphoma can be differenti-ated from IOP (ADC range 1.02 - 2.28×10 −3 mm2/s) with100 % accuracy using an ADC threshold of 1.0×10−3mm2/sand an ADC ratio of less than 1.2×10−3mm2/s [9–12, 68].Similarly, lymphomas show significantly lower ADC values

Fig. 13 80-year-old male patient with lymphoma of the right orbit. a.Axial T1W image of the orbits shows a hypointense, well-demarcatedanterior conal-extraconal lesion (arrow). Axial T2W (b) and coronalSTIR (c) images demonstrate intermediate signal intensity of the bulkymass (arrows). Note homogenous aspect. ADC map (d) reveals restricteddiffusion (arrow) with very low ADC values (ADC=0.6×10 −3 mm2/s)characteristic of lymphoma. Axial contrast enhanced T1W image (e)

shows homogenous enhancement of the mass (arrow). There isenhancement of the superior rectus muscle (thin arrow) suggestingpossible involvement. However, the ADC map clearly shows that thesuperior rectus muscle has no restricted diffusion (thin arrows in d ande). f. Coronal fused PET and STIR image from FDG PET/MRI revealshigh tracer uptake within the mass (SUVmean=4.8, SUVmax=6.7). Noother lymphoma manifestations were detected in the body


as compared to Ig-G4 related disease (mean ADC 1.67×10 −3

mm2/s) [69] as well as metastases (ADC range 0.9-1.6×10 −3

mm2/s) [9, 10, 12]. In a study by Haradome et al, the meanADC and contrast-enhancement ratio of orbital lymphomas

was found to be significantly lower than that of benign OLPD,thereby aiding in their differential diagnosis [70].

Sarcoidosis may mimic lymphoma at clinical presentationand at cross-sectional imaging. Sarcoidosis is a chronic,

Fig. 14 35-year-old female patient with painful proptosis, loss of vision,and subcutaneous facial swelling. Biopsy of the face performed in anoutside institution suggested inflammatory pseudotumour. a. CoronalSTIR image shows an ill-defined, moderately hyperintense lesioninvolving the entire left orbit (asterisk) and encasing the optic nerve(thin arrow). The subcutaneous hyperintense, poorly defined area on theleft (hollow arrow) corresponds to the biopsied region. b. Axial contrast-enhanced FS T1WMR image of the same patient as in a. The left orbitallesion shows diffuse post-contrast enhancement (asterisk). Enhancingsoft tissue is seen extending along the left superior orbital fissure intothe left cavernous sinus (arrow) and the dura along the left greater wingof sphenoid. c.Axial contrast-enhanced FS T1W image at the level of themaxillary sinus demonstrates perineural spread along the pterygopalatine

fossa and maxillary nerve (arrows). Hollow arrows in b and c point atextra-orbital involement. d. ADC map reveals restricted diffusion of theorbital lesion with very low ADC values (ADC=0.7×10 −3 mm2/s)suggesting lymphoma. The optic nerve shows even lower ADC values(thin arrows) due to compression and ischemia. e.Colour coded DTI mapshows major reduction of FA values in the left optic nerve (thin arrows).FA values were 0.4–0.5 on the left and 0.56–0.58 on the right. f. FDGPET/CT demonstrates high tracer uptake in the orbit (asterisk), along thesuperior orbital fissure and in the cavernous sinus and sphenoid (arrows)confirming findings revealed in b. SUVmean=10, max=16. Otherhypermetabolic lesions were found in the neck nodes, mediastinum, andabdomen. Biopsy of orbital contents revealed NHL

Fig. 15 Two different patientswith FD involving the facial andorbital bones. Characteristicground-glass appearance(asterisks) and expansion of themedullary cavity is seen in bothcases on NECT. In b, bonyexpansion of the right sphenoidwing and of the right anteriorclinoid process causes severenarrowing of the right optic canal(arrow), thereby requiringdecompressive surgery


multisystemic, granulomatous disorder which commonly in-volves the orbit. It can cause mass-like lacrimal gland andmuscle infiltration (often bilateral), optic nerve thickening

and enhancement or pseudotumoural intra-orbital masses.There may be associated intracranial extension. The imagingfindings may be exactly similar to lymphoma, even on DWI

Fig. 16 64-year-old female patient with headache and left vision lossunderwent MRI. a. Axial T2W image of the orbits shows deformityand expansion of the sphenoid body. The medullary cavity is replacedby tissue with mixed hyperintense (thick arrow)–hypointense (thin arrow)signal. b. Axial T1W image of the same patient shows the lesion to bemainly isointense to brain parenchyma (thick arrow) and with stronglyhypointense central areas (thin arrow). On the left, there are hyperintenseperipheral regions. c. Axial contrast-enhanced T1W image showsinhomogeneous contrast enhancement (thick arrow) and cystic portions

(dashed arrow). d. ADC map reveals increased diffusion (ADC=2.3×10−3 mm2/s) suggesting a benign lesion (thick arrow). FD was suspected. e.Oblique reformatted axial image from 3D T2W sequence showscompression of the left optic nerve (thin arrow) at the level of the opticcanal. f.Axial NECT image shows ground-glass appearance and irregularossification of the involved bones. Part of the lesion was resected todecompress the right optic nerve. Histology revealed psammomatousvariant of FD

Fig. 17 15-year-old girl with a left orbital VLM. a.Axial FS T2W imageshows a mutliloculated cystic lesion involving the intraconal andextraconal compartments of the left orbit (arrow). The strongly

hypointense septae of the VLM show hemosiderin staining. b. Contrast-enhanced FS T1W MR image of the same patient shows minimalenhancement (arrow) along the intervening septae of the VLM


[12]. Bilateral hilar adenopathy, lung lesions, and elevatedserum angiotensin-converting enzyme levels point to sarcoid-osis. Often, a biopsy is required to demonstrate the non-caseating granulomas of sarcoidosis.

Lymphomas commonly show high FDG uptake (Figs. 13and 14). Whole body PET CT has become part of standardstaging of orbital lymphomas and is probably usedmore wide-ly for this disease than any other orbital tumour Although,low-grade MALT lymphomas may show relatively low FDGuptake, PET CT has shown very good results in the detectionof systemic metastases of even low-grade orbital lymphomas,which were not detected by conventional imaging [18, 20, 71,72]. MRI PET holds promise in evaluating post-treatmentresponse of lymphomas, especially in children [22, 73].

Bone and sinus compartment

Fibrous dysplasia (FD)

FD is a developmental disorder of the bone in which normalbone marrow is replaced by fibro-osseous tissue with expan-sion of the medullary cavity. Cranio-facial fibrous dysplasia iscommonly involves the frontal, ethmoid or sphenoid bones. Itis typically seen in children and adolescents with slight femalepredilection. FD is monoostotic in 70-80 % cases and

polyostotic in the rest. Orbital bony involvement leads tohypertelorism, exophthalmos, visual impairment and blind-ness. Surgery is needed to correct facial deformity or severeoptic nerve compression [1, 26, 51].

FD shows replacement of lamellar bone with abnormalmetaplastic immature woven bone, forming irregular curvilin-ear trabeculae on histology; this appearance has been de-scribed as “Chinese characters” or alphabet soup. The fibrousportion contains bland spindle cells without significant mitoticactivity. Haemorrhage and cystic changes may be seen [26,51].

Radiographs and CT shows bony expansion with Bgroundglass^ appearance (Fig. 15). There may be consequentnarrowing of the optic nerve canal and impingement of theoptic nerve (Figs. 15 and 16). The fibrous stroma and osteoidmaterial typically appears hypointense on T1W images(Fig. 16). On T2W images the signal intensity may be low(18-38 % cases), intermediate (18 %) or high (62–64 %)(Fig. 16). Marked enhancement may be seen on CEMRI [1,51] (Fig. 16), as well as fluid-fluid levels. Similar to benignlesions elsewhere in the head and neck, FD shows significant-ly higher ADC values compared to malignant bone tumours[74, 75] (Fig. 16).

FD can appear hypermetabolic on PET CTwith high SUVvalues thereby simulating malignancy [76, 77]. Nevertheless,

Fig. 18 28-year-old female patient with NF-1. MRI was performed forpre-surgical planning. Coronal STIR (a) and axial T2W (b) images showpoorly circumscribed, serpentine masses (asterisks) within the rightorbital conal-extraconal and preseptal compartments. Findings aretypical of an OPNF. There is associated dural ectasia of the right opticnerve sheath. Classic right-sided sphenoid wing dysplasia is also noted

(arrow). The ADCmap (c) shows no restriction of diffusion (ADC=1.3×10−3 mm2/s) in keeping with the benign histology. d. Axial contrast-enhanced FS T1W image shows heterogeneous strong contrastenhancement of the OPNF (arrow). Axial (e) and sagittal (f) DTI 3Dtractography views show complete disorganization of fibres within theOPNF surrounding the globe and optic nerve


the high ADC values and the characteristic CT aspect help toavoid this pitfall.

Multi-compartmental tumours

Venolymphatic malformation (VLM)

VLM, also called lymphangioma, is a congential,hamartomous vascular malformation with variable lymphoidand venous vascular elements. It is hemodynamically isolatedfrom systemic drainage. VLM accounts for 5 % of paediatricorbital tumours; about 60% cases are diagnosed by 16-20 yearsof age. It is commonly extraconal; however, it can be intraconalor multicompartmental. Proptosis, diplopia, and optic neurop-athy are common presenting symptoms. Sudden increase inproptosis indicates haemorrhage within the lesion. Unlike cap-illary hemangiomas, which involute over time, VLM growwith the patient, especially in puberty. Treatment is usuallyconservative. Percutaneous sclerotherapy is performed in selectcases. Surgery is difficult due to the transpatial nature and alsodue to risk of recurrence [2, 4, 26, 45, 60].

VLM typically contain irregular shaped venous and lym-phatic channels lines by flattened endothelial cells and inter-spersed connective tissue. The cystic spaces may show bloodproducts or lymphatic fluid within [26, 45, 60]. VLM areusually seen on CT and MRI as poorly circumscribed, lobu-lated, transpatial lesions. Hemorrhagic and proteinaceous con-tents may appear hyperdense on NECT. Fluid-fluid levels arecommonly seen. Calcification and bony erosions are

uncommon. The lesion shows variable signal on T1W andT2W MR images (Fig. 17). As against capillary hemangi-omas, flow voids are absent. Fat-saturated CEMRI imagesare ideal for mapping the lesion. Rim enhancement is com-monly seen (Fig. 17) [2, 4, 26, 45, 60]. VLM show increaseddiffusion [13]. Their ADC values have been reported in therange of 1.44–1.53×10 −3 mm2/s and 1.75-2.2×10 −3 mm2/s[9, 12]. On FDG PET CT, there is no focal uptake.

Orbital plexiform neurofibroma (OPNF)

OPNF is a hamartoma of neuroectodermal origin accountingfor 1-2 % of all orbital tumours, typically arising in the firstdecade of life. OPNF is diagnostic of NF-1. OPNF can in-volve any peripheral nerve, but the sensory nerves of the orbitare commonly involved. It is usually associated with otherfindings of NF-1 such as ONG, sphenoid wing dysplasia,and buphthalmos. OPNF usually presents with nodularperiorbital masses, loss of vision, and proptosis. The infiltra-tive serpentine masses extend in both the intraconal andextraconal compartments. Progressive glaucoma, optic nerveatrophy, and blindness are eventual complications. The risk ofmalignant sarcomatous degeneration is about 10%. ONSF areusually not amenable to surgery; however, debulking may benecessary for preservation of vision or cosmetics [4, 26, 78].

Unlike schwannomas, it is not possible to distinguish hostnerve fibres separately from OPNF. The host nerve fasciclesare irregularly expanded by myxoid accumulation, tumourousSchwann cells, fibroblasts, and collagen fibres [26]. Plain

Fig. 19 35-year-old femalepatient with left histologicallyproven orbital IOP. a. Axial T2Wimage shows a plaque-likehypointense extraconal lesion(arrowhead), adjacent to thelateral rectus muscle. Lymphomawas considered as an imagingdifferential. b. ADC map of theorbits of the same patient showsanADC value of 1.1×10−3 mm2/s(arrowhead), which is higher thanthe ADC value expected forlymphoma. c. Axial PET/CTimage of the same patient showshigh FDG uptake within thelesion (arrow) (SUVmean=5,SUVmax=6) mimickinglymphoma


Fig. 20 50-year-old male patientwith biopsy-proven IgG4-RD ofthe right orbit. Coronal bone-window CT image of the orbits(a) shows a well-circumscribed,extraconal, soft tissue-densitymass located inferomedially in theright orbit. It is associated withbony erosion of the laminapapyracea (arrow). b. Axial T2Wimage of the same patient showsvery low signal within the well-circumscribed lesion (arrow).Note that it is lower than usuallyseen in lymphoma. c. Axialcontrast-enhanced FS TIW imageshows homogeneous non-specificenhancement within the lesion(arrow). d. ADC map showsrestricted diffusion (ADC=0.9×10 −3 mm2/s)

Fig. 21 Two different patients with orbital metastases. a – c. 74-year-oldfemale patient with diplopia and a history of melanoma of the scalp7 years previously. T2W (a), unenhanced FS T1W (b) and contrast-enhanced FS T1W (c) images of the orbits shows a conal-extraconalmass in the left orbit (arrows) and a second mass with similar imagingfeatures in the suprazygomatic right masticator space (short arrows). Thestrongly hyperintense signal in b (arrows) suggests the presence ofhaemorrhage and/or melanin. Imaging findings are strongly suggestiveof metastases from melanoma. Findings were confirmed by biopsy. d – f.71-year-old female patient with known breast cancer. d. Axial CECT

image shows a well-circumscribed enhancing mass in the left orbit inextraconal location (arrow). e. Coronal STIR image of the same patientshows non-specificmoderately high signal of themetastatic deposit (thickarrow). Thin arrow points to the left optic nerve. f. Axial PET/CT imageof the same patient shows physiological high FDG uptake in the extra-ocular muscles making it difficult to detect the metastatic lesion (arrow).As the imaging findings in this case are non-specific, the diagnosis oforbital metastasis can be suggested only when the clinical background isknown. Biopsy confirmed metastasis from breast cancer


radiography may detect a classical defect in the greater wing ofsphenoid called BHarlequin eye^ appearance. Both CTandMRIshow the characteristic orbital and periorbital infiltrative soft tis-sue masses, associated OPNF, and sphenoid wing dysplasia(Fig. 18). On T2W MRI, the nodular masses typically appearhyperintense with central low signal called the Btarget sign^. Thenodular masses show variable post contrast enhancement(Fig. 18). MRI is ideal for evaluation of the associated intracra-nial abnormalities. Infantile/capillary hemangioma, VLM, andRMS may mimic OPNF on imaging; however, the other associ-ated stigmata of NFI are absent in these cases [4, 78].

OPNF show mixed or increased diffusion [13]. DTI withtractography reconstruction is increasingly being used for thepre-operative mapping of neurogenic tumours originating inthe head and neck (typically from the brachial plexus), such asschwannomas and neurofibromas [79–81]. DTI withtractography reconstruction can accurately detect alterationsof involved nerve fascicles, such as displacement, stretching,bowing, or rupture (Fig. 18). FDG-PET CTand more recentlyMRI PET are sensitive and specific tools to detect sarcoma-tous transformation in OPNF [82, 83].

Inflammatory orbital pseudotumour (IOP)

IOP is the most common cause of a painful orbital mass inadults and the third most common orbital disease after thyroid

ophthalmopathy and lymphoproliferative disorders. IOP is abenign, non-infective, inflammatory condition without identi-fiable local or systemic causes and is typically seen in the 4th-6th decade. The disease may present as scleritis, uveitis, lac-rimal adenitis, myositis, perineuritis, or diffuse orbital inflam-mation. The classic clinical triad consists of unilateral orbitalpain, proptosis, and impaired ocular movement. There may beassociated fibrosing mediastinitis or retroperitoneal fibrosis.The diagnosis of IOP is made after exclusion of other pathol-ogies like thyroid ophthalmopathy, lymphoma, Wegener’sgranulomatosis, and sarcoidosis. Treatment with steroidsshows dramatic response, which helps to confirm the diagno-sis [1, 2, 68, 84, 85].

IOP is characterized histologically by a mixed inflam-matory infiltrate, which consists of lymphocytes, plasmacells, macrophages, and eosinophilia. Fibrosis may alsobe seen [84, 85]. Imaging findings may be non-specific.CT and MRI may show mass-like enhancing soft tissuewithin the orbit, streaky fat stranding, lacrimal gland en-hancement, and optic nerve sheath enhancement (Fig. 19).The extraocular muscles are commonly enlarged andshow enhancement. These inflammatory masses are usu-ally hypointense to fat on T1W images and iso-hypointense on T2W images (Fig. 19). They can extendto involve the pterygopalatine fossa, nasopharynx, andcavernous sinus [1, 2, 68, 84, 85].

Fig. 22 60-year-old male patient with desmoplastic melanoma of theright eyelid. a. Axial T2W image shows a heterogeneous signal-intensity lesion involving the subcutaneous tissue of the right lateralcanthus (big arrow) with an infiltrating component extending into theextraconal compartment of the right orbit. There is suspicious invasionof the muscle cone and the globe (short arrow). b: Axial T1W image of

the same patient does not show hyperintense signal within the lesion inkeeping with low melanin content. c. Coronal contrast-enhanced FS TIWimage reveals avid enhancement within the lesion. d. Axial PET/CTimage of the same patient shows high FDG uptake within the lesiondue to high glucose metabolism. No other lesions were detected in therest of the body


IOP is a great imaging mimic of several other pathol-ogies. These include other causes of myositis (thyroidophthalmopathy, infective cellulitis) and other T2-hypointense infiltrative lesions (lymphoma, IgG4-RD,and granulomatous diseases). Thyroid ophthalmopathycauses bilateral inflammation of the extra-ocular muscles,commonly involves the inferior and medial rectus mus-cles, often spares the myo-tendinous junctions, and is as-sociated with elevated thyroid-stimulating hormonelevels. IgG4-RD can show similar features as thyroidophthalmopathy, however, with normal thyroid stimulat-ing hormone levels. Infective cellulitis is commonly asso-ciated with fever, leukocytosis, and abscess formation.Clinical features such as pain, conjunctival congestion,and eyelid oedema help to distinguish IOP from lympho-ma, which commonly presents with a painless palpablemass [1, 2, 68, 84–88]. As described previously, ADCvalues help to accurately differentiate between IOP andlymphoma (Fig. 19) [9–12, 68]. IOP has been reportedto show very high FDG uptake mimicking malignancy(Fig. 19) [89, 90].

IgG4-RD

Immunoglobulin G4-related disease (IgG4-RD) is achronic, systemic autoimmune, fibro-inflammatory condi-tion. Its most common manifestation is autoimmune pan-creatitis; however, retroperitoneal fibrosis, sclerosingcholangitis, interstitial nephritis, periarteritis, Riedel’s thy-roiditis, chronic dacryoadenitis, Mikulicz disease, and cer-tain orbital inflammatory pseudotumours may frequentlybe encountered. As with IOP, IgG4-RD shows a dramaticresponse to corticosteroid therapy, although spontaneousresolution has been described [85–88]. Practically anypart of the orbit can be involved, and the typical histolog-ical features, regardless of the affected site, are denselympho-plasmacytic infiltration with abundant IgG4-positive plasma cells, storiform-type fibrosis with obliter-ative phlebitis [86–88].

On MRI, IgG4-RD typically demonstrates significanthypointensity on T1 and T2W images with marked enhance-ment after contrast administration. Lymphoma shows similarMRI features on conventional sequences (Fig. 20) [86–88].As described previously, DWI with ADC mapping may helpto differentiate between the two pathologies (Fig. 20) [69].PET CT can help to detect extra-pancreatic involvement inIgG4-RD [91].

Metastases

Metastases represent the most common orbital malignan-cy. Common sources for orbital metastases include mela-nomas , breas t and lung cancers in adul t s , and

neuroblastomas in children. Metastases commonly in-volve the orbital bones and extraconal compartment; how-ever, they may also involve the choroid. Painful proptosisis the most common presentation, the exception beingc i r r ho t i c b r e a s t c a r c i noma me t a s t a s e s , whe r eenophthalmos is a typical finding due to rectus muscleinfiltration and contraction [1, 2, 4].

Orbital metastases show histology typical to the primarytumour. High mitoses and necrosis may be seen (Fig. 21).When the primary tumour is unknown, immunohistochemis-try may aid in diagnosis.

CT and MRI may show an enhancing infiltrativeextraconal mass (Fig. 21). There can be associated bonydestruction. Choroidal metastases from melanoma mayappear hyperdense on NECT and hyperintense on T1WMR images. CEMRI also helps to detect associated intra-cranial metastases [1, 2, 4]. As described previously, me-tastases can mimic lymphomas on conventional CT/MRsequences. DWI can help to differentiate between the two[9, 10, 12]. An orbital metastatic deposit may be inciden-tally diagnosed for the first time on a PET CT. PET CTcan also help to detect the primary tumour site and met-astatic deposits to other organs [17–19].

Lid tumours with orbital extension

Common malignant tumours of the eyelid include squa-mous cell carcinoma (SCC), basal cell carcinoma, mela-noma, sebaceous cell carcinoma, and lymphoma. Thesetumours are often highly aggressive and show contiguousinvasion of orbital structures. About 43 % of SCC of theeyelid show orbital involvement (Fig. 22). Perineuralspread along the branches of the trigeminal nerve is alsocommon. Orbital exenteration is required for controllinglocal disease spread which may be relentless and poten-tially fatal. Cross-sectional imaging helps in the localstaging of the disease [18, 92, 93]. PET CT plays a valu-able role in detecting local nodal and distant metastasesfrom eyelid carcinomas [18, 59].

Conclusion

Evaluation of orbital masses requires a multimodality ap-proach to balance the strength and weaknesses of each modal-ity. Combining accurate clinical information with appropriateimaging modalities and being aware of potential diagnosticpearls and pitfalls helps to obtain the best results. Future ad-vances in functional imaging are likely to make a significantimpact on ophthalmological cancer imaging.We hope that thisreview has satisfactorily served the purpose of highlightingthese points.


Grants and conflict of interest information No conflicts of interest

Open Access This article is distributed under the terms of the CreativeCommons At t r ibut ion 4 .0 In te rna t ional License (h t tp : / /creativecommons.org/licenses/by/4.0/), which permits unrestricted use,distribution, and reproduction in any medium, provided you give appro-priate credit to the original author(s) and the source, provide a link to theCreative Commons license, and indicate if changes were made.

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